Electron beam switching tube reset means



Feb. 4, 1964 J. R. SMITH ETAL 3,120,624

ELECTRON BEAM SWITCHING TUBE RESET MEANS Filed Sept. 2, 1960 2 Shaets-$heet 1 I20 [I26 REsET RESET l24 INPUT CIRCUIT /|2e /|O4 /|l4 /H6 BEAM SWITCHING BEAM SWITCHING BEAM SWITCHING ,[22 TUBE STAGE TUBE STAGE TUBE STAGE I II n l I06 *108 H0 H2 H8 02 rlOO i INPUT MULTIVIBRATOR MULTIVIBRATOR I MULTIVIBRATOR SIGNAL DRIVER FOR STAGE DRIVER FOR STAGE DRIVER FOR STAGE I II n i 236 I INVENTORS.

? 1 JAMES RSM/TH l FREDERICK E. 2066 RESET ATTORNEY Feb. 4, 1964 J. R. SMITH ETAL 3,120,624

ELECTRON BEAM SWITCHING TUBE RESET MEANS. Filed Sept. 2, 1960 2 Sheets-Sheet 2 t; 1 f f '15 VOLTS I I I I I I T'o l I I 80 f sPAnss I/ 40 II To ZERO 20 T SPADES l AE o I 20 g j I I I I 40 I l I so I I I I I l I TIME IN MICRO-SECONDS United States Patent 3,120,624 ELECTRON BEAM SWITCHING TUBE RESET MEANS James R. Smith and Frederick E. Zogg, Webster, N.Y.,

assignors to General Dynamics Corporation, Rochester,

N.Y., a corporation of Delaware Fiied Sept. 2, 1960, Ser. No. 53,790 5 Claims. (Cl. 315-85) This invention relates to means for resetting electron beam switching tubes and, more particularly, to means capable of reliably and very quickly resetting a large plurality of electron beam switching tubes.

Electron beam switching tubes, such as the type 6700 electron beam switching tube manufactured by Burroughs Corporation, are well known in the art. Briefly, an electron beam switching tube is a magnetron having a single centrally-located cathode surrounded by a plurality, such as ten, of separate anodes. Individual to each anode is a switching grid member and a spade member. An electron beam may be set up between the cathode and any single one of the anodes. In response to an input pulse, the electron beam may be switched from this single anode to the next following anode. Depending upon the polarity of the applied magnetic field, this switching may take place either in a clockwise or a counterclockwise direction. Thus, it will be seen that an electron beam switching tube may be utilized as a ring counter. B cascading a plurality of electron beam switching tubes, a counter for counting any number of significant figures may be constructed. Furthermore, some equipment may include several separate groups of cascaded electron beam switching tubes, so that the total number of electron beam switching tubes utilized in such equipment may be quite large.

It is often desirable to clear all of a large plurality of beam switching tubes simultaneously and reset the electron beam of each of these tubes to manifest zero value. Furthermore, where consecutive groups of data are to be applied to the beam switching tubes in rapid succession, it is necessary that the time required to reset the tubes to manifest zero value be a minimum.

The reset means utilized by the prior art for resetting electron beam switching tubes has at least two distinct disadvantages. First, this prior art reset means provides reliable resetting only for a maximum of two or three electron beam switching tubes. Thus, it is not possible to utilize a single prior art reset means to reliably control the simultaneous resetting of a large plurality of electron beam switching tubes. Second, the prior art reset means utilizes a thyratron, which, due to its inherent ionization and de-ionization times, limits the maximum speed at which resetting of the electron beam switching tubes may take place.

It is, therefore, an object of the present invention to provide a reset means which is capable of resetting a large plurality of electron beam switching tubes.

It is a further object of the present invention to provide a reset means for electron beam switching tubes which is capable of operating at a very high speed.

These and other objects, features and advantages of the present invention will become apparent from the following detailed description taken together with the accompanying drawings, in which:

FIG. 1 is a block diagram showing the association of 3,120,624 Patented Feb. 4, 1964 "ice the reset circuit with a multistage beam switching tube counter along with the drivers individually associated with each stage of the counter,

FIG. 2 is a schematic diagram of a typical beam switchin-g tube stage along with a schematic diagram of the driver stage individually associated therewith,

FIG. 3 is a schematic diagram of the reset circuit contemplated by the present invention, and

FIG. 4 is a graph illustrating the waveform of the respective outputs produced by the reset circuit of FIG. 3.

Referring to FIG. 1, an input signal, consisting of a series of pulses, is applied to a multivibrator driver for stage I over conductor 10-2. Multivibrator driver for stage I 100, in response to alternate pulses of the input signal, applies a first input to beam switching tube stage I 104 over conductor 106-, and, in response to the remaining pulses of the input signal, applies a second input to beam switching tube stage I 10 4 over conductor 108.

Beam switching tube stage I 104, in response to each complete cycle thereof, produces an output pulse on conductor 1 10, which forms the input signal to multivibrator driver for stage II 112, which is identical in structure and function to multivibrator driver for stage I 100. Beam switching tube for stage II 114, which is identical in structure and function to beam switching tube stage II 104, and multivibrator driver for stage II 112 are associated in a manner identical to that described above.

In addition to beam switching tube stages 104 and 114, there may be included a large plurality of similar beam switching tube stages, only the last of which, beam switching tube stage n 11 6, is specifically shown. Associated with each additional beam switching tube stage, such as beam switching tube stage n 116, is an individual multivibrator driver for that stage, such as multivibrator driver for stage n 118. Each additional beam switching tube stage has an input pulse applied thereto in response to each complete cycle of the immediately preceding beam switching tube stage.

When it is desired to reset all the beam switching tube stages to a zero value, a reset input is applied as an input to reset circuit and is also applied in multiple to the multivibrator driver for each stage, as shown, over conductor 122.

In response to a reset input applied to reset circuit 120, reset circuit .1 20 applies a first reset signal having a first particular waveform to the zero spades of all the beam switching tube stages in multiple over conductor 124, and applies a second signal having a second particular waveform to all the spades of the non-zero spades of all the beam switching tube stages in multiple over conductor 12-6. in addition, reset circuit 120 provides a grid bias potential for each beam switching tube stage which is applied thereto in multiple over conductor 128.

Referring now to FIG. 2, there is shown a schematic circuit of one of the beam switching tube stages, such as beam switching tube stage I 104, and one of the multivibrator driver stages, such as multivibrator driver for stage I 100. Electron beam switching tube 200 includes a single cathode 202, which, as shown, is connected to point of reference potential through resistance 204, bypassed by capacitance 206. Further included are ten separate anodes 208-0, 208-1 208-9, respectively. Although for the purposes of clarity in the drawing, anodes 208-0 208-9 are shown in a linear array, in an actual electron \J beam switching tube they are circumferentially disposed about cathode 202 in the form of a ring, so that anode 208-9 is followed by anode'208-0. Each of anodes 208- 208-9, respectively, is connected to a point of positive potential, as shown, through an individual resistance, such as resistances 210-0 210-9, all of which are connected in series with common resistance 212. Resistance 2 12 is bypassed by capacitance 214. The output from the beam switching tube stage is taken from anode 208-0.

Individually associated with each anode is a spade, such as spades 216-0 216-9, respectively. The potential on conductor .124 from reset circuit 120, shown in FIG. 1, is applied to zero spade 216-0 through resistance 218-0, which is bypassed by capacitance 220-0. The potential on conductor 126 from reset circuit 120, shown in FIG. 1, is applied to each of the non-zero spades, 216-1 216-9 through respective resistances 218-1 218-9, individually associated, as shown, with each of these non-zero spades. Each of the respective resistances 218-1 218- 9 is individually bypassed by respective capacitances 220- 1 220-9. Also individually associated with each anode of electron beam switching tube 200 is a grid, such as grid 222-0 222-9. The bias potential on conductor 128 from reset circuit 120, shown in FIG. 1, is applied to the zero grid 220-0 and to each of the other evenly numbered grids through resistance 224, and is applied to each of the odd numbered grids through resistance 226.

The schematic cicuit of driver stage 100, included in FIG. 2, shows that driver stage 100 is nothing more than a conventional bistable multivibrator, sometimes called a flip-flop. In one stable state, tube 228 is rendered conducting and tube 230 is rendered non-conducting. In the other stable state, tube 228 is rendered non-conducting and tube 230 is rendered conducting. In response to a first pulse applied as an input signal to multivibrator driver 100, multivibrator 100 is switched from one stable state thereof to the other and then in response to the next following pulse applied as an input signal to multivibrator driver 100, multivibrator driver 100 is switched back from this other state to its original state, this process being repeated in response to each additional pulse applied as an input signal to multivibrator driver 100.

A signal proportional to the change in the output voltage of tube 228, as it is switched from a conducting to a non-conducting state or from a non-conducting to a conducting state, is coupled to the odd numbered grids of electron beam switching tube 200- through capacitance 232. In a similar manner, a signal proportional to the change in the output voltage of tube 230 as it is switched from a non-conducting to a conducting state or from a conducting to a non-conducting state, is coupled to the even numbered grids of electron beam switching tube 200 through capacitance 234.

The reset input on conductor 122 is applied, as shown, to the control electrode of tube 230 through negatively poled diode 236 to insure that tube 230 is cut off and tube 228 is conducting immediately following reset.

Referring now to FIG. 3, there is shown a schematic diagram of reset circuit 120. As shown, reset circuit circuit 120 includes a first triode 300, from which the zero spade bus potential on conductor 124 is derived, and triode 302, from which the non-zero spade bus potential on conductor 126 is derived. More specifically, both triodes 300 and 302, respectively, are connected as cathode followers with anode 304 of triode 300 and anode 306 of triode 302 connected directly to a point of positive potential. Cathode 308 of triode 300 is connected to a point of reference potential through resistance 310 and cathode 312 of triode 302 is connected to the point of reference potential through resistance 314.

Further included in reset circuit 120 is a voltage divider composed of resistances 316, 318, and 320, respectively, which are connected, as shown, in series between the point of positive potential and the point of reference potential. Resistance 320-is bypassed by capacitance 322 2 and serially connected resistances 318 and 320 are bypassed by capacitance 324.

The direct current potential appearing at the junction of resistances 318 and 320 is applied to conductor 128 to provide the grid bias potential for the electron beam switching tubes.

The direct current potential appearing at the junction of resistances 316 and 318 is applied to control electrode 326 of triode 300 through resistance 328 and is applied to control electrode 330 of triode 302 through resistance 332.

The reset input on conductor 122 is applied to control electrode 326 of triode 300 through capacitance 334 and is applied to control electrode 330 of triode 302 through capacitance 336.

The respective values of resistance 328 and capacitance 334 are made substantially larger than the respective values of resistance 332 and capacitance 336, so that the time constant formed by capacitance 334 and resistance 328 is substantially longer than the time constant formed by capacitance 336 and resistance 332.

The reset input is also applied to the zero spade bus conductor 124 through capacitance 338 and is applied to the non-zero spade bus conductor 126 through capacitance 340.

Considering now the operation of the present inven tion, a small inter-electrode and stray capacitance exists between each spade and the point of reference potential. Although the inter-electrode and stray capacitance between any particular spade and the point of reference potential is negligibly small, the total inter-electrode and stray capacitance which exists between zero spade bus conductor 124 and the point of reference potential and between spade bus conductor 126 and the point of reference potential when a large plurality of beam switching tube stages are utilized becomes significantly large.

Referring again to FIG. 3, triodes 300 and 302 are normally heavily conductive. This results in a relatively large voltage drop across cathode resistance 310 of triode 300, placing a relatively high positive potential on zero bus conductor 124. In a similar manner, the relatively high voltage drop across cathode resistance 314 of triode 302 places a relatively high positive potential on non-zero spade bus conductor 126. As shown in FIG. 4, for a typical reset circuit, the positive potential on each of conductors 124 and 126 is approximately volts.

This results in the above-mentioned inter-electrode and stray capacitance between the spades of the several tubes being charged to this positive potential of approximately 100 volts.

The reset input applied to conductor 122 consists of a negative pulse having a very steep leading edge and a relatively slowly rising lagging edge. This steep leading edge is applied to grid 326 of triode 300 through capacitance 334 and to grid 330 of triode 302 through capacitance 336, causing triodes 300 and 302 to be cut off.

If capacitances 338 and 340 were not present, the cutting oit of triodes 300 and 302 would result in the potential on conductors 124 and 126 dropping down to zero potential. However, due to the accumulated one hundred volt positive charge on the inter-electrode and stray capacitance between the spades of the various beam switching tube stages, discussed above, the potential on the spades would drop to zero potential relatively slowly, as determined by the discharge time constant of the significantly large total inter-electrode and stray capacitance through resistances 310 and 314, respectively. This would result in unreliable clearing and resetting of the beam switching tube stages.

The presence of capacitances 338 and 340 overcomes this problem by providing a low impedance path which practically instantaneously absorbs the accumulated positive charge on the inter-electrode and stray capacitance. Furthermore, capacitances 338 and 340 apply the steep leading edge of the reset input directly to conductors 124 and 126. Thus, as shown in FIG. 4, in response to the steep leading edge of the reset input, the potential on zero spade bus conductor 124 drops instantaneously to 60 volts at time and the potential on non-zero spade bus conductor 126 drops instantaneously to -40 volts at time t This results in the electron beams of all the beam switching tube stages being reliably broken at time t,, even when a large plurality of beam switching tube stages are employed.

Immediately following the steep leading edge of the reset input, capacitance 338 will begin to charge in a positive direction at a rate determined by the time constant of capacitance 338 and resistance 310 and capacitance 334 will begin to charge in a positive direction at a rate determined by the time constant of capacitance 334 and resistance 328. Also, capacitance 340 will tend to charge in the positive direction at a rate determined by the time constant of capacitance 340 and resistance 314, and capacitance 336 will tend to charge in the positive direction at a rate determined by the time constant of capacitance 33-6 and resistance 332.

As stated above, the time constant of capacitance 334 and resistance 328 is substantially longer than the time constant of capacitance 336 and resistance 332.

Therefore, as shown in FIG. 4, at a time t when cathode 312 of triode 302 and non-zero spade bus conductor 126 have risen to a potential of 20 volts, control electrode 330 of triode 392 will have risen to a potential relative to cathode 312 thereof to permit triode 302 to resume conduction. As capacitance 336 continues to charge in a positive direction, triode 302 conducts more and more heavily, resulting in the potential on non-zero spade bus conductor rising along the curve shown in FIG. 4, until at time it, it again reaches its normal positive potential of approximately 100 volts.

Due to the longer time constant of capacitance 334 and resistance 328, triode 300 is not rendered conductive until time t;;, and then the potential on zero spade bus conductor 125 rises more slowly to its normal positive potential of approximately 100 volts, reaching it at time t During the period between times t and t when both triodes 300 and 302 have been rendered conductive, a potential difference AE exists between zero spade bus conductor 124 and non-Zero spade bus conductor 126, with zero spade bus conductor 124 at a relatively negative potential with respect to non-zero spade bus conductor 126. This potential difference AB is sufiicient to insure that the electron beams of the respective beam switching tube stages re-forms to the respective zero spades thereof.

When the spades of a large plurality of beam switching tube stages are connected in parallel to conductors 124 and 126, the input impedance thereto becomes extremely low. This has the tendency to cause unreliable resetting of the beam switching tube stages. However, since triodes 300 and 302 are connected as cathode followers, when triodes 300 and 302 are conducting, the output impedance thereof is also extremely low. The low output impedances make possible the reliable resetting of a large plurality of beam switching tube stages (seven or more), which would otherwise be impossible.

As can be seen from FIG. 4, the total time needed by the reset circuit of the present invention to reset a large plurality of beam switching tube stages is only 40 microseconds.

Although the reset circuit disclosed herein utilizes vac uum tube cathode followers, it is obvious that it is within the skill of the art to substitute transistor emitter followers therefor. Furthermore, although only a preferred embodiment of the present invention has been shown and described herein, it is not intended that the invention be restricted thereto, but that it be limited by the true spirit and scope of the appended claims.

What is claimed is:

1. A plurality of electron beam switching tube stages, wherein the tube of each stage includes a first spade and a plurality of second spades, and wherein each stage ineludes an individual capacitively bypassed resistance coupled to each spade of each tube, said tubes being rendered in operative condition in response to a given first potential being applied to each spade of each tube through said bypassed resistance individual thereto; the combination therewith of a reset circuit therefor comprising first means including a first time constant circuit for normally producing an output of said given first potential, second means for applying the output of said first means in multiple to said first spade of each of said tubes through the bypassed resistance individual thereto, third means including a second time constant circuit for normally producing an output of said given first potential, fourth means for applying the output of said third means in multiple to each of said second spades of each of said tubes through the bypassed resistance individual thereto, said first time constant circuit having a substantially longer time constant than said second time constant circuit, and fifth means coupled to said first and third means for intermittently applying a reset pulse having a steep leading edge as an input to said first and third means to effect a substantially instantaneous drop in the respective outputs of said first and third means to at least a given negative potential with respect to said given first potential sufficient to break the electron beam of each of said tubes, the potential of the output of said first means returning to said given first potential at a rate determined by the time constant of said first time constant circuit and the potential of the output of said third means returning to said given first potential at a rate determined by the time constant of said second time constant circuit, whereby an electron beam to said first spade of each tube will be instituted.

2. The combination defined in claim 1, wherein said first and third means each has a low output impedance with respect to said individual resistances.

3. The combination defined in claim 1, wherein said first means includes a first cathode follower and said third means includes a second cathode follower, and wherein said output of said first means is obtained from the output of said first cathode follower and said output of said third means is obtained from the output of said second cathode follower.

4. The combination defined in claim 3, wherein said first cathode follower includes a first control electrode, a first resistance of a given magnitude connected to said first control electrode for applying a given bias potential thereto to render said first cathode follower normally heavily conductive, a first capacitance of a given magnitude coupling said fifth means to said first control electrode for applying said steep leading edge of said reset pulse to said first control electrode to render said first cathode follower non-conductive, wherein said second cathode follower includes a second control electrode, a second resistance of a given magnitude connected to said second electrode for applying said given bias potential thereto to render said second cathode follower normally heavily conductive, a second capacitance of a given magnitude coupling said fifth means to said second electrode for applying said steep leading edge of said reset pulse to said second control electrode to render said second cathode follower non-conductive, and wherein the time constant formed by said first resistance and said first capacitance is substantially longer than the time constant formed by said second resistance and said second capacitance.

5. The combination defined in claim 4, wherein said first cathode follower further includes a first cathode, a third resistance connecting said first cathode to a point of reference potential, and a third capacitance having a magnitude which is high relative to the interelectrode capacitance of said first spades of all said tubes coupling said fifth means to said first cathode for applying said steep leading edge of said reset pulse to said first cathode, said output of said first means being derived from said 7 first cathode, and wherein said second cathode follower further includes a second cathode, a fourth resistance connecting said second cathode to said point of reference potential, and a fourth capacitance having a magnitude which is high relative to the interelectrode capacitance of 5 all said second spades of all said tubes coupling said fifth means to said second cathode for applying said steep leading edge of said reset pulse to said second cathode,

said output of said third means being derived from said second cathode.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PLURALITY OF ELECTRON BEAM SWITCHING TUBE STAGES, WHEREIN THE TUBE OF EACH STAGE INCLUDES A FIRST SPADE AND A PLURALITY OF SECOND SPADES, AND WHEREIN EACH STAGE INCLUDES AN INDIVIDUAL CAPACITIVELY BYPASSED RESISTANCE COUPLED TO EACH SPADE OF EACH TUBE, SAID TUBES BEING RENDERED IN OPERATIVE CONDITION IN RESPONSE TO A GIVEN FIRST POTENTIAL BEING APPLIED TO EACH SPADE OF EACH TUBE THROUGH SAID BYPASSED RESISTANCE INDIVIDUAL THERETO; THE COMBINATION THEREWITH OF A RESET CIRCUIT THEREFOR COMPRISING FIRST MEANS INCLUDING A FIRST TIME CONSTANT CIRCUIT FOR NORMALLY PRODUCING AN OUTPUT OF SAID GIVEN FIRST POTENTIAL, SECOND MEANS FOR APPLYING THE OUTPUT OF SAID FIRST MEANS IN MULTIPLE TO SAID FIRST SPADE OF EACH OF SAID TUBES THROUGH THE BYPASSED RESISTANCE INDIVIDUAL THERETO, THIRD MEANS INCLUDING A SECOND TIME CONSTANT CIRCUIT FOR NORMALLY PRODUCING AN OUTPUT OF SAID GIVEN FIRST POTENTIAL, FOURTH MEANS FOR APPLYING THE OUTPUT OF SAID THIRD MEANS IN MULTIPLE TO EACH OF SAID SECOND SPADES OF EACH OF SAID TUBES THROUGH THE BYPASSED RESISTANCE INDIVIDUAL THERETO, SAID FIRST TIME CONSTANT CIRCUIT HAVING A SUBSTANTIALLY LONGER TIME CONSTANT THAN SAID SECOND TIME CONSTANT CIRCUIT, AND FIFTH MEANS COUPLED TO SAID FIRST AND THIRD MEANS FOR INTERMITTENTLY APPLYING A RESET PULSE HAVING A STEEP LEADING EDGE AS AN INPUT TO SAID FIRST AND THIRD MEANS TO EFFECT A SUBSTANTIALLY INSTANTANEOUS DROP IN THE RESPECTIVE OUTPUTS OF SAID FIRST AND THIRD MEANS TO AT LEAST A GIVEN NEGATIVE POTENTIAL WITH RESPECT TO SAID GIVEN FIRST POTENTIAL SUFFICIENT TO BREAK THE ELECTRON BEAM OF EACH OF SAID TUBES, THE POTENTIAL OF THE OUTPUT OF SAID FIRST MEANS RETURNING TO SAID GIVEN FIRST POTENTIAL AT A RATE DETERMINED BY THE TIME CONSTANT OF SAID FIRST TIME CONSTANT CIRCUIT AND THE POTENTIAL OF THE OUTPUT OF SAID THIRD MEANS RETURNING TO SAID GIVEN FIRST POTENTIAL AT A RATE DETERMINED BY THE TIME CONSTANT OF SAID SECOND TIME CONSTANT CIRCUIT, WHEREBY AN ELECTRON BEAM TO SAID FIRST SPADE OF EACH TUBE WILL BE INSTITUTED. 